The present invention relates to a liquid crystal display module capable of suppressing changes in the gap for the liquid crystal layer in a liquid crystal display module, where a liquid crystal panel is mounted on a package, thereby displaying high quality images, and also relates to a projection-type liquid crystal display device.
Liquid crystal panels are widely used as display devices for television receivers, monitors for information equipment such as personal computers, etc. and other various display means. In such a liquid crystal panel, a driving electrode serving as a power supply electrode for pixel selection or as a power supply electrode for a switching element is provided on one of a pair of substrates, and a common electrode is provided on another substrate, these two substrates being opposed to each other while making these two electrodes face each other, and a liquid crystal layer is provided into the resulting gap between the bonded substrates.
A small size, high precision liquid crystal panel using P-Si (polysilicon) TFT is known as a typical small size, high precision liquid panel applicable to an image-forming means for a projection-type liquid crystal display device, a view finder for video camera or head-mount display, etc.
It is also known to provide a common electrode on a transparent substrate and a driving electrode on a silicon substrate, provide a liquid crystal layer or a liquid crystal layer of polymer dispersion type into the gap between the opposed substrate and encase the resulting liquid crystal panel in a package to make a module.
Conventional mounting of a liquid crystal panel on a package for making a module is based on a package structure having an opening in a display region to enclose two substrates therein, where the liquid crystal panel and the package are fixed to each other by an adhesive.
In a small size liquid crystal panel for use in such a type of module, terminals of a flexible printed substrate are connected to the corresponding lead terminals provided by patterning on one side of the driving substrate of the liquid crystal panel to supply power at various desired voltages to the driving electrode, whereas power to the common electrode is supplied through a conductive paste provided between the common substrate and the driving substrate.
FIG. 8 is an expanded perspective view showing a typical structure of the conventional small size liquid crystal panel, and FIG. 9 is a cross-sectional view along line IX--IX of FIG. 8.
In FIGS. 8 and 9, numeral 1 denotes a transparent substrate (common substrate, which may be hereinafter also referred to as first substrate), 1a a transparent common electrode formed on the inner surface of the first substrate, 2 a silicon substrate (driving substrate, which may be hereinafter also referred to as second substrate), 2a pixel electrodes formed on the inner surface of the second substrate, 3 a liquid crystal layer, 4 a seal for sealing the liquid crystal between the first substrate and the second substrate, 6 an adhesive layer of ultraviolet-curing adhesive, thermosetting resin adhesive, silver paste or the like, 7 a package of ceramics or plastics, 9 a flexible printed substrate, 5 contacts and 2b connection terminals.
In case of the conventional liquid crystal display module, the recess surface of package 7 and second substrate 2 are fixed to each other by adhesive layer 6, as shown in FIG. 9. In case of a polymer dispersed liquid crystal panel using a silicon substrate as second substrate 2, second substrate 2 is fixed to package of ceramics by a silver paste as used in die bonding.
Liquid crystal layer 3 provided in a space between first substrate 1 and second substrate 2 is driven by an electric field developed between individual pixel electrodes 2a in a pixel area and common electrode 1a. Generally, connection terminals 2b are provided on second substrate 2 and voltages for driving the individual pixel electrodes, etc. are supplied thereto externally. Voltage is also supplied to common electrode 1a on the first electrode 1, but since those similar to connection terminals 2b are not provided on the first substrate 1, wiring conductors are provided between a predetermined part of connection terminals 2b and contacts 5, so that electrical connection to common electrode 1a of first substrate 1 is made at contact 5. For this electrical connection, conductive paste as a conductive adhesive such as silver paste, etc. which is a conductive connection member.
FIG. 10 is a cross-sectional view showing one typical structure of applying to a dichroic prism, a reflection-type liquid crystal display module whose liquid crystal panel is fixed to the package, as shown in FIG. 9, where a numeral 1 designates a first substrate, 2 a second substrate, 6 an adhesive, 7 a package, 26 a dichroic prism, 27 a reflection-type liquid crystal display module and 31 an optical paste.
In FIG. 10, second substrate 2 is fixed to package 7 by thermosetting adhesive layer 6 to make a reflection-type liquid crystal display module, and first substrate 1 is closely fixed to dichroic prism 26 by optical paste 31.
Silicone oil, etc. whose refractive index is approximately equal to that of dichroic prism 26, are used as optical paste 31 to prevent generation of reflected light at the boundary between first substrate 1 and dichroic prism 26, and prevent the resulting light intensity loss, projected image contrast decrease, etc.
FIG. 11 is a schematic view of an optical system showing a typical projection-type liquid crystal display device using a liquid crystal display module, where numeral 20 designates a light source, 21 a parabolic mirror, 22 a condenser lens, 23 a reflector mirror, 24 a first aperture, 25 a lens, 26 a dichroic prism, 27R a reflection-type liquid crystal display module for red, 27G a reflection-type liquid crystal display module for green, 27B a reflection-type liquid crystal display module for blue, 28 a second aperture, 29 a projector lens and 30 a screen.
The structure of projection-type liquid crystal display device, as shown in FIG. 11 will be explained below.
Reflection-type liquid crystal display module for red 27R, reflection-type liquid crystal display module for green 27G and reflection-type liquid crystal display module for blue 27B are closely applied to three faces of dichroic prism 26, respectively, by optical paste 31 as explained referring to FIG. 10 and fixed thereto by a fixing means (not shown in the drawing) after positional adjustment so as not to be out of their right positions. These reflection-type liquid crystal display modules must be firmly fixed to the dichroic prism so that they may not be deviated from their right positions due to vibrations or shocks during working or transportation of the projection-type liquid crystal display devices. Thus, a means of pressing the respective reflection-type liquid crystal display modules 27R, 27G and 27B against the dichroic prism is used as the fixing means.
In the projection-type liquid crystal display device with such a structure, light from light source 20 is made parallel beams by parabolic mirror 21, and then enters dichroic prism 26 as incident light through condenser lens 22, reflector mirror 23, first aperture 24 and lens 25.
The incident light is split into three colors, i.e. red, green and blue, by dichroic prism 26, and the split colors enter as incident light reflection-type liquid crystal display module for red 27R, reflection-type liquid crystal display module for green 27G and reflection-type liquid crystal display module for blue 27B, each of which is fixed to the three faces of dichroic prism 26, respectively.
Images are formed on each of reflection-type liquid crystal display modules for red 27R, reflection-type liquid crystal display module for green 27G and reflection-type liquid crystal display module for blue 27B by signals supplied through said flexible printed substrate 9, and the incident light is modulated by the formed images. Reflected lights from the modules 27R, 27G and 27B are combined by dichroic prism 26 and emitted through lens 25.
Such reflection-type liquid crystal display modules can take a scattering state or a reflection state for each pixel according to image signals and can emit mirror reflections through said lens 25. The combined light to three colors emitted through lens 25 passes through the second aperture, whereby scattered lights, among reflected lights, are shut off from the scattering sites in the display region or from the circumference of the display region to project the combined light onto screen 30. Since a uniform dark state area is formed at the circumference of the display region, an image display of high image quality can be obtained. In this manner, full color images of high quality synthesized from the respective color images formed on said reflection-type liquid crystal display module for red 27R, reflection-type liquid crystal display module for green 27G and reflection-type liquid crystal display module for blue 27B can be reproduced on screen 30.